E-Flora BC: Electronic Atlas of the Flora of British Columbia

Astragalus canadensis var. mortonii L. (Nutt.) S. Watson
Canadian milk-vetch (Morton's Canadian milkvetch)
Fabaceae (Pea family)

Introduction to Vascular Plants
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Distribution of Astragalus canadensis var. mortonii
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Species Information

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Robust perennial herb from a spreading rhizome, greenish and nearly glabrous to greyish with basally 2-forked hairs; stems 1-few together, erect to decumbent, simple or branched above, 0.3-1 m tall.
Alternate, pinnately compound, 10-20 (35) cm long; leaflets 13 to 29, elliptic to oblong, blunt or notched and tiny-pointed at the tip, 1.5-4 cm long, often glabrous above; stipules membranous-papery, 6-15 mm long, some or all fused and sheathing at the base, the free ends lanceolate and long-tapering.
Inflorescence a spike-like, axillary raceme of 30 to 150, nodding, downward overlapping, pea-like flowers, the racemes 5-15 cm long on stalks 5-20 cm long; corollas greenish-white to cream, 12-17 mm long, the wings equal to the banner, the keel often purple-tipped; calyces 6-10 mm long, finely appressed-hairy, the tube twice as long as the awl-shaped teeth.
Pods, erect on stubs 1-2 mm long, crowded and persistent on the erect stalk of the inflorescence, cylindric, 8-20 mm long, with a tiny hook at the tip, somewhat leathery or stiff-papery, often finely appressed-hairy, 2-chambered.
Three varieties are recognized for BC. The two varieties in S BC are sympatric and freely intergradient.

1. Pods cylindric, not grooved beneath and usually hairless; plants of NE BC..................... var. canadensis

1. Pods grooved beneath and usually hairy; plants of S BC.

2. Calyces white- and black-hairy; the teeth nearly equal in size, 1.5-3 mm long; plants greenish, not silvery-hairy...................... var. mortonii (Nutt.) S. Wats.

2. Calyces white-hairy, the teeth 1-2 mm long, the upper pair broader and shorter than the lower three; plants more or less silvery-hairy.....................var. brevidens (Gandog.) Barn.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Mesic to dry open forests, thickets, meadows, streambanks and lakeshores in the steppe and montane zones; common in NE BC (var. canadensis) and S BC east of the Coast-Cascade Mountains (vars. brevidens and mortonii); var. canadensis - N to NT, E to PQ and S to AR, VA and TX, var. brevidens - S to SD, ND, CO and CA, var. mortonii - S to ID, MT and N WA.

Source: The Illustrated Flora of British Columbia


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Astragalus mortonii Nutt.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References